Use bookmark creation date fallback for 6 weeks after installing M54

components/ntp_snippets/bookmarks/bookmark_suggestions_provider.h

Index: components/ntp_snippets/bookmarks/bookmark_suggestions_provider.h
diff --git a/components/ntp_snippets/bookmarks/bookmark_suggestions_provider.h b/components/ntp_snippets/bookmarks/bookmark_suggestions_provider.h
index 1f2aabd146a4e65863de12dedf7a31f9c24dfc00..f8b4aea3f90c7208ab08dd4fcdbb5c80be83fa03 100644
--- a/components/ntp_snippets/bookmarks/bookmark_suggestions_provider.h
+++ b/components/ntp_snippets/bookmarks/bookmark_suggestions_provider.h
@@ -14,6 +14,9 @@
 #include "components/ntp_snippets/category_status.h"
 #include "components/ntp_snippets/content_suggestions_provider.h"
 
+class PrefRegistrySimple;
+class PrefService;
+
 namespace gfx {
 class Image;
 }
@@ -26,9 +29,12 @@ class BookmarkSuggestionsProvider : public ContentSuggestionsProvider,
  public:
   BookmarkSuggestionsProvider(ContentSuggestionsProvider::Observer* observer,
                               CategoryFactory* category_factory,
-                              bookmarks::BookmarkModel* bookmark_model);
+                              bookmarks::BookmarkModel* bookmark_model,
+                              PrefService* pref_service);
   ~BookmarkSuggestionsProvider() override;
 
+  static void RegisterProfilePrefs(PrefRegistrySimple* registry);
+
  private:
   // ContentSuggestionsProvider implementation.
   std::vector<Category> GetProvidedCategories() override;
@@ -99,6 +105,11 @@ class BookmarkSuggestionsProvider : public ContentSuggestionsProvider,
   base::Time node_to_change_last_visit_date_;
   base::Time end_of_list_last_visit_date_;
 
+  // TODO(jkrcal): Remove this and the pref when it's not needed anymore.

[Marc Treib, 2016/08/19 11:41:12]

s/when it's not needed anymore/after M55/
Be as specific as possible with this kind of TODO. Chances are the details will
get forgotten, and at some point in the far future someone will wonder if this
thing is still needed.

[Philipp Keck, 2016/08/19 12:49:52]

Done.

+  // For six weeks after first installing M54, this is true and the
+  // fallback implemented in BookmarkLastVisitUtils is activated.
+  bool creation_date_fallback_;
+
   DISALLOW_COPY_AND_ASSIGN(BookmarkSuggestionsProvider);
 };